Z-axis measurement fixture and method of determining the planarity of objects using the fixture

ABSTRACT

A Z-axis measurement fixture used for testing whether a chemical reagent test slide exhibits Z-axis variability, which may affect measurements performed by an automated chemical analyzer using such test slides, includes a planar main body that holds three stainless steel balls, each ball having a known and calibrated diameter. Portions of the stainless steel balls extend outwardly from the top wall and the bottom wall of the planar main body. A chemical reagent test slide is placed on the fixture to rest on and be supported at three points by the portions of the stainless steel balls which project outwardly from the top wall of the planar main body. The fixture is placed on the surface of a gauge block of an optical measurement system such that the lower portions of the three stainless steel balls will rest on the gauge block of the optical measurement system.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is related to U.S. Provisional Patent Application Ser.No. 63/085,283, filed on Sep. 30, 2020, and titled “Z-Axis MeasurementFixture And Method Of Determining The Planarity Of Objects Using TheFixture”, the disclosure of which is hereby incorporated by referenceand on which priority is hereby claimed.

BACKGROUND Technical Field

The present disclosure is directed to fixtures used in calibration andquality control measurements of planar objects to check for Z-axisvariability or imperfections in the surface topography of such objects,and more particularly relates to quality control measurements performedon chemical reagent test slides used by automated chemical analyzers.

Background

In reflectometry, absorbance and fluorescence measurements of drychemistry reagent test slides performed by an automated chemicalanalyzer such as the VetTest® analyzer, the Catalyst Dx® analyzer andthe Catalyst One® analyzer (each of which is manufactured and/ordistributed by IDEXX Laboratories, Inc. of Westbrook, Me.) and Vitros®analyzers (available from Ortho Clinical Diagnostics of Raritan, N.J.),it is important that the test slides used in such measurements performedby the analyzers are not warped during manufacture, storage orinappropriate handling such that they vary in thickness, exhibitimperfections in their surfaces or are not entirely planar over allportions thereof. Indeed, Z-axis variability in the test slides, orirregularities in the surface topography of such slides, especially overcritical portions thereof where measurements are taken, will have adeleterious effect on the accuracy of such measurements.

OBJECTS AND SUMMARY

Some analyzers include a rotating carousel having slots in which thereagent test slides are respectively received. Loading the test slideson the carousel is performed in an automated process by the analyzer. Ifa test slide is warped, it may not be properly received in itsrespective slot on the carousel, causing the carousel to jam andrequiring the clinician to clear the jam, resulting in down time andpossible the loss of a test run.

In accordance with good quality control practices, IDEXX Laboratories,Inc. continually performs tests on such slides to ensure that,lot-to-lot, such slides consistently reside in a single X-Y plane(within acceptable tolerances) and do not manifest any Z-axisvariability that may affect measurements performed using such slides oraffect the operation and performance of the instrument in which suchslides are used.

To perform such quality control tests on the slides to check for Z-axisvariability, a jig or fixture can be used to hold the slide in place torest on a gauge block of a measurement system (also referred to hereinas a “measurement instrument”), for example, an optical measurementinstrument, such as the Micro-Vu™ analyzer manufactured by Micro-VuCorporation of Windsor, Calif. However, conventional fixtures used insuch quality control tests, which fixtures are often made from a plasticmaterial, may themselves have imperfections in their overall thicknessesand lack planar consistency over all areas thereof such that the holdingfixture may contribute to inaccurate Z-axis measurements in qualitycontrol tests performed on the slides. Slides are also placed to restdirectly on the gauge block of the optical measurement, but it has beenfound that in some instances the slides do not rest evenly on the gaugeblock, the result of which is inaccurate quality control measurements.

More generally, when testing a planar object to accurately measureZ-axis variability or irregularities in the surface of the object,whether the objects are chemical reagent test slides, as mentionedpreviously, or semiconductor wafers, cast products and consumable testproducts having critical flatness requirements, sheet metal products orthe like, it is essential to establish datum points. Furthermore, partsthat are free form or have irregular shapes are next to impossible toestablish such datum points when held in a conventional test fixture foroptically or visually performed quality control tests.

It is an object of the present disclosure to provide a fixture forholding a planar object so that accurate tests may be performed to checkthe planar object for Z-axis variability or surface irregularities.

It is another object of the present disclosure to provide a fixture forholding a planar object in a precise position in an optical measurementsystem used in optically testing the planar object for Z-axisvariability or surface irregularities.

It is still another object of the present disclosure to provide afixture used in quality control tests performed on a planar object heldthereby and having a free form or irregular shape.

It is a further object of the present disclosure to provide a fixturefor holding a chemical reagent test slide to check the slide for Z-axisvariability or surface irregularities that may affect measurementsperformed by an automated chemical analyzer using such a reagent testslide.

It is yet a further object of the present disclosure to provide afixture for holding a planar object for quality control tests performedon the planar object which overcomes the inherit disadvantages ofconventional fixtures which, when used to hold a planar object, may leadto inaccurate measurements obtained during such quality control tests.

It is still a further object of the present disclosure to provide amethod of determining the planarity of an object using a Z-axismeasurement fixture on which the object may be mounted.

It is another object of the present disclosure to provide a method fortesting whether a planar object exhibits Z-axis variability or surfacetopography irregularities.

In accordance with one form of the present disclosure, a Z-axismeasurement fixture used for testing whether a planar object exhibitsZ-axis variability or surface topography irregularities includes aplanar main body, or spacer, and a plurality of object supportingmembers. The planar main body has a top wall and a bottom wall disposedopposite the top wall. The planar main body has formed through thethickness thereof a plurality of member receiving openings extendingbetween the top wall and the bottom wall.

Each of the object supporting members has a known and calibrateddimension in at least one coordinate direction, and each objectsupporting member is received by a respective member receiving openingformed in the planar main body. In one form, each object supportingmember may be spherical in shape, and may be a stainless steel ballhaving a known and calibrated diameter.

Each object supporting member has a first portion which projectsoutwardly from the top wall of the planar main body, and a secondportion which projects outwardly from or is at least level with thebottom wall of the planar main body. Each object supporting member isarranged within its respective member receiving opening such that thefirst portion thereof projecting outwardly from the top wall of theplanar main body and the second portion thereof projecting outwardlyfrom or being level with the bottom wall of the planar main body are inalignment with the known and calibrated dimension of the objectsupporting member in the at least one coordinate direction. The firstportion of each object supporting member projecting outwardly from thetop wall of the planar main body is adapted to contact and support aportion of the planar object, and the second portion of each objectsupporting member projecting outwardly from or being level with thebottom wall of the planar main body is adapted to contact and rests on asurface of a gauge block of an optical measurement system.

Having the planar object to be tested for quality control and Z-axisvariability supported directly by the object supporting members having aknown and calibrated dimension, and the object supporting membersresting on the surface of the gauge block of an optical measurementsystem, ensures that the planar object, whether it is a chemical reagenttest slide, sheet metal or a semiconductor wafer or the like, issupported above the gauge block of an optical measurement system by aprecise and calibrated distance so that the fixture itself will notcause any inaccurate optical or visual measurements of Z-axisvariability or surface irregularities obtained during quality controltests.

These and other objects, features and advantages of the presentdisclosure will be apparent from the following detailed description ofillustrative embodiments thereof, which is to be read in connection withthe accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a top plan view of one form of a Z-axis measurement fixtureformed in accordance with the present disclosure, and structured forholding trapezoidially-shaped chemical reagent test slides thereon forquality control testing.

FIG. 1A is a top plan view of the Z-axis measurement fixture shown inFIG. 1, and showing a trapezoidially-shaped chemical reagent test slidemounted thereon.

FIG. 2 is a top perspective view of the Z-axis measurement fixture shownin FIG. 1 having a chemical reagent test slide mounted thereon andpositioned for testing in an optical measurement system.

FIG. 3 is a diagrammatic side view of the fixture shown in FIGS. 1 and 2supporting a chemical reagent test slide and being shown mounted on agauge block of an optical measurement system.

FIG. 4 is another perspective view of the fixture shown in FIGS. 1-3having a chemical reagent test slide mounted thereon and beingpositioned under a camera of an optical measurement system for qualitycontrol testing.

FIG. 5 is top plan view of a chemical reagent test slide mounted on theZ-axis measurement fixture, and illustrating preferred targets on theslide viewed by the optical measurement system in testing for Z-axisvariability or surface irregularities in the slide.

FIG. 6A is a side view of a chemical reagent test slide being opticallytested for Z-axis variability in a conventional manner, that is, byplacing the reagent test slide directly on the surface of a gauge blockof an optical measurement system.

FIG. 6B is a graph illustrating optical measurements performed at asingle point (Point 7—see FIG. 5) of a chemical reagent test slideplaced directly on the gauge block of an optical measurement system in aconventional measurement technique such as shown in FIG. 6A.

FIG. 7A is a side view of a chemical reagent test slide being mounted ona fixture formed in accordance with the present disclosure and opticallytested for Z-axis variability in the slide, the fixture having the testslide mounted thereon being placed on the surface of a gauge block of anoptical measurement system.

FIG. 7B is a graph illustrating optical measurements performed at asingle point (Point 7—see FIG. 5) of a chemical reagent test slidemounted on the fixture of the present disclosure, the fixture having thetest slide mounted thereon being placed on the gauge block of an opticalmeasurement system such as shown in FIG. 7A.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Z-axis variability or lack of flatness in planar objects 2 (FIG. 1A) mayaffect the quality of the object 2 (FIG. 1A) or the accuracy ofmeasurements taken using such planar objects 2 when planarity orflatness is a critical feature. For example, with respect to chemistryslides 4 (FIG. 1A), flatness and outer dimensions are important featureswhen such slides 4 are used in chemistry analyzers. Flatness is alsocritical in microtiter plates and other consumable products that areused in and function with other test instruments. Certain sheet metalparts are required to be flat with minimal surface irregularities orimperfections so that they may properly align with other components inthe final assembly of a product. Post processing of semiconductor wafersstringently requires flatness in the wafers. Cast products may furtherhave critical flatness requirements. The Z-axis measurement fixture 6 ofthe present disclosure, as will be described in greater detail herein,may be used to verify the flatness and planarity of such objects 2 (FIG.1A).

FIG. 1 illustrates one form of the Z-axis measurement fixture 6 of thepresent disclosure. This fixture 6 is particularly designed to test forZ-axis variability in trapezoidially-shaped chemical reagent test slides4, such as the slide 4 shown mounted on the fixture 6 in FIG. 1A, thatare used by chemical analyzers and other instruments manufactured and/ordistributed by IDEXX Laboratories, Inc. Fixture 6 can also be used totest for Z-axis variability in generally rectangular-shaped chemicalreagent test slides, such as those used in the Vitros® and VetTest®analyzers. However, the use of the measurement fixture 6 of the presentdisclosure is not limited to the testing of such chemical reagent testslides 4, and is applicable for testing many different forms of planarobjects 2 including free form or irregularly-shaped planar objects 2.

With reference to FIG. 1, the exemplary Z-axis measurement fixture 6shown therein includes a planar main body 8, and a plurality of objectsupporting members 10. The planar main body 8 has a top wall 12 and abottom wall 14 (FIG. 3) that is disposed opposite the top wall 12. Theplanar main body 8 defines a plurality of member receiving openings 16extending between the top wall 12 and the bottom wall 14.

The planar main body 8 may take on many different shapes to accommodateplanar objects 2 of different sizes and shapes, including free form orirregular shapes. Furthermore, another advantage of the fixture 6 of thepresent disclosure is that the planar main body 8 may be easily andcost-effectively fabricated from a plastic or thermoplastic material ona 3D printer or by injection molding. 3D printing or injection moldingthe fixture 6 may introduce irregularities in the surfaces of the mainbody 8 of the fixture 6. As will become evident from the followingdescription of the fixture 6, such irregularities in the surfaces of themain body 8 will not affect quality control tests performed on a planarobject 2, such as a chemical reagent test slide 4, supported by andmounted on the fixture 6 of the present disclosure to check for Z-axisvariability in the planar object 2. This is because the planar object 2does not rest directly on the planar main body 8 of the fixture 6, aswill be described below.

As mentioned above, the Z-axis measurement fixture 6 of the presentdisclosure includes a plurality of object supporting members 10. Eachobject supporting member 10 has a known and calibrated dimension in atleast one coordinate direction. For example, the object supportingmembers 10 may be spherical objects or stainless steel balls 18 having aknown and calibrated diameter. However, such object supporting members10 may take on other shapes, such as cylindrical posts or rods having anaxial length or radius that is known and calibrated, egg-shaped or ovalsupports, or pyramid or conically-shaped structures, each of which has aknown and calibrated dimension in at least one coordinate direction (forexample, from the base of the cone or pyramid to the apex thereof).

Each object supporting member 10, whether it is a stainless steel ball18, a rod-shaped support, or another structure having a calibrateddimension, is received by and retained in a respective member receivingopening 16 formed in the planar main body 8 of the fixture 6. Moreparticularly, each object supporting member 10 has a first portion 20which projects outwardly from the top wall 12 of the planar main body 8,and a second portion 22 which projects outwardly from or is at leastlevel with the bottom wall 14 of the planar main body 8. Even moreparticularly, each object supporting member 10 is arranged within itsrespective member receiving opening 16 such that the first portion 20thereof projecting outwardly from the top wall 12 of the planar mainbody 8 and the second portion 22 thereof projecting outwardly from orbeing level with the bottom wall 14 of the planar main body 8 are inalignment with the known and calibrated dimension of the objectsupporting member 10 in the at least one coordinate direction. Forexample, a stainless steel ball 18 will have a known and calibrateddimension in any radial direction. If a rod or post is used as theobject supporting member 10, where the axial length of the rod or postis known and calibrated, a portion of one axial end of the rod or postwill extend outwardly from the top wall 12 of the planar main body 8 ofthe fixture 6, and a portion of the opposite axial end of the rod orpost will extend outwardly from or be level with the bottom wall 14 ofthe planar main body 8. Or, if the diameter of the rod or post is knownand calibrated, the rod or post may be placed sideways in a respectivemember receiving opening 16 such that diametrically opposite portions ofthe cylindrical surfaces of the rod or post project outwardly from thetop wall 12 and project outwardly or are level with the bottom wall 14of the planar main body 8.

In one form of the fixture 6 of the present disclosure, the planar mainbody 8 holds the object supporting members 10 captive within theirrespective member receiving openings 16 in an immobile or mobile state.In some embodiments, the object supporting members 10 are movable withintheir member receiving openings 16 in a transverse direction through thethickness of the planar main body 8, that is, between the top wall 12and the bottom wall 14 thereof. In some embodiments, the dimensions ofthe member receiving openings 16 may be selected so that the objectsupporting members 10 received thereby are removable therefrom fromeither the top wall 12 or the bottom wall 14 of the planar main body 8,or may “float” within their respective member receiving openings 16 andnot be constrained in movement in the transverse direction by the planarmain body 8 of the fixture 6.

For example, and as shown in FIG. 3 of the drawings, the memberreceiving openings 16 extending between the top wall 12 and the bottomwall 14 of the planar main body 8 may be generally cylindrical in shapeand, preferably, have a relatively larger diameter upper portion 24 inproximity to the top wall 12 that extends into the thickness of theplanar main body 8, and a smaller diameter lower portion 26 (relative tothe diameter of the upper portion 24) in proximity to the bottom wall 14and which extends partially into the thickness of the planar main body8. In this embodiment of the fixture 6, the inside diameters of theupper portions 24 of the member receiving openings 16 are chosen to beslightly greater than the lateral width or diameter of the objectsupporting members 10 (for example, the stainless steel balls 18 shownin FIG. 3) such that the object supporting members 10 may be received byand are movable in the upper portions 24 of the member receivingopenings 16. The inside diameters of the lower portions 26 of the memberreceiving openings 16 are chosen so that the second portions 22 of theobject supporting members 10 may project outwardly from or are at leastlevel with the bottom wall 14 of the planar main body 8, as shown inFIG. 3 of the drawings.

FIGS. 2-4 show how the Z-axis measurement fixture 6 of the presentdisclosure may be used in conjunction with an optical measurement system28 for checking Z-axis variability in a planar object 2, in thisexample, a trapezoidially-shaped chemical reagent test slide 4. Theoptical measurement system 28 includes a gauge block 30 which ispositioned underneath a viewing camera 32. The gauge block 30 has aknown flat surface 34. The planar object 2 to be measured for Z-axisvariability is mounted on the fixture 6, and the fixture 6 is placed onthe calibrated surface 34 of the gauge block 30 of the opticalmeasurement system 28 and positioned in the corner of a right angle form36 used with the optical measurement system 28. The second portions 22of the object supporting members 10 contact and rest on the surface 34of the gauge block 30. The planar object 2 to be tested for Z-axisvariability rests in contact with and is supported by the first portions20 of the object supporting members 10. Thus, the planar main body 8 ofthe fixture 6 holds the object supporting members 10, be they sphericalballs, rods or some other structure, in an X/Y plane but allows theobject supporting members 10 to freely contact the planar object 2 andthe known flat surface 34 of the gauge block 30. Thus, the use ofcalibrated object supporting members 10, such as stainless steel balls18, eliminates the requirement for tight tolerances on the planar mainbody 8 of the fixture 6 and allows the main body 8 to be custom printedfor a particular application, that is, to support planar objects 2 ofdifferent shapes, such as, for example, trapezoidially-shaped chemicalreagent test slides 4, or free form or irregularly-shaped objects 2. Theuse of such object supporting members 10, providing a known andcalibrated “Z” distance from the flat surface 34 of the gauge block 30of the optical measurement system 28, results in more accuratemeasurements of Z-axis variability in the planar object 2 being testedand enables the planar object 2 to be positioned in space byconsistently contacting a plurality of target datums on the planarobject 2 (such as three points on the chemical reagent test slide 4 whenthree calibrated stainless steel balls 18 are used).

One method of measuring Z-axis variability in a planar object 2, in thisparticular example, a chemical reagent test slide 4, will now bedescribed. A measurement fixture 6 formed in accordance with the presentdisclosure and including features described herein is placed on thesurface 34 of a gauge block 30 of an optical measurement instrument 28,such as the Micro-Vu™ instrument mentioned previously, and under thecamera 32 of the optical measurement instrument 28, and is aligned in anX-Y plane on the gauge block 30 by placing the fixture 6 against theright angle form 36. The object supporting members 10, which preferablyare three spaced apart, calibrated stainless steel balls 18, are held inplace in an X-Y plane by the main body 8 of the fixture 6 but areallowed free contact with the surface 34 of the gauge block 30 of theoptical measurement instrument 28.

A chemical reagent test slide 4 is mounted on the fixture 6 and held inplace thereon by object edge guide projections 38 and wedge projections40 situated on the main body 8 of the fixture 6, as will be described ingreater detail. The test slide bottom surface 56 contacts the threecalibrated balls 18 of the fixture 6 and is oriented in the Z-axis tothe plane made by the three points of contact with the calibrated balls18.

Optical measurements of the slide 4 are taken by the optical measurementinstrument 28 by establishing a zero reference plane from the focalpoint of the camera 32 at a selected point or area on the top surface 54of the slide 4, the camera 32 preferably being adjusted to have apredetermined field of view and/or a predetermined focal plane inestablishing the zero reference plane at the desired point or area onthe slide 4.

More specifically, and with reference to FIG. 5 of the drawings, severalspaced apart points on the top surface 54 of the planar object 2 areselected for viewing by the camera 32 of the optical measurementinstrument 28. For example, in testing a trapezoidially-shaped chemicalreagent test slide 4 for flatness, such as the test slide 4 shown inFIG. 5, preferably eight focus points are selected about the peripheryof the slide 4. One point on the slide 4, for example, at Position “1”shown in FIG. 5, is designated as the focal point used to establish azero reference plane. The camera 32 of the optical measurementinstrument 28 then successively focuses on each of the other points onthe top surface 54 of the slide 4, e.g., at Positions “2”-“8” shown inFIG. 5, but not necessarily in the numerical order which is shown, andthe optical measurement instrument 28 measures the distance of the topsurface 54 of the slide 4 at each focal point relative to theestablished zero reference plane at the selected starting point (e.g.,at Position “1”). Some focal points on the slide 4 may reside in an X-Yplane above or below the zero reference plane. If no focal points arebelow the zero reference plane, then the degree of flatness of the slide4 is determined as the highest measurement (i.e., the largest distanceabove the zero reference plane). Similarly, if no focal points are abovethe zero reference plane, then the degree of flatness of the slide 4 isdetermined as the lowest measurement (i.e., the largest distance belowthe zero reference plane). If one or more focal points are above thezero reference plane and one or more focal points are below the zeroreference plane, then the absolute values of the highest measurement andthe lowest measurement are added together in determining the degree offlatness of the slide 4.

It should be realized, of course, that in the method described above,the slide 4 or other object 2 may be mounted on the measurement fixture6 before or after the measurement fixture 6 is placed on the gauge block30 of the optical measurement instrument 28 and positioned under theviewing camera 32. Furthermore, use of the right angle form 36 ispreferred to properly position the fixture 6 on the optical measurementinstrument 28, but the form 36 in some instances may not be needed.

FIG. 5 illustrates preferred measurement targets (shown by the numbers1-8) on the trapezoidially-shaped reagent test slide 4 supported by thefixture 6 of the present disclosure that are viewed optically by thecamera 32 of the optical measurement system 28.

FIGS. 6A and 6B illustrate the results of Z-axis variabilitymeasurements taken on a chemical reagent test slide 4 that restsdirectly on the gauge block 30 of an optical measurement system 28 in aconventional measurement method rather than being mounted on the Z-axismeasurement fixture 6 of the present disclosure. As can be seen fromFIG. 6B, there are some inaccuracies in the optical measurements atPoint 7 on the slide 4 (see FIG. 5 for the location of this targetpoint) when the chemical reagent test slide 4 rests directly on thegauge block 30 in such a conventionally-practiced method for checkingfor Z-axis variability.

However, reference should now be had to FIGS. 7A and 7B of the drawings,which show the chemical reagent test slide 4 being supported by themeasurement fixture 6 of the present disclosure and, more specifically,resting on the object supporting members 10 (e.g., the stainless steelballs 18) of the measurement fixture 6, the supporting members 10 havinga known and calibrated dimension in at least one coordinate direction(e.g., the diameters of the stainless steel balls 18). It should benoted that it is the object supporting members 10 (e.g., the calibratedballs 18) that support the planar object 2 above the surface 34 of thegauge block 30 by a precise distance that is unaffected by anyirregularities in the planar main body 8 of the fixture 6 used inholding the object supporting members 10. As shown in FIG. 7B, a moreaccurate measurement of Z-axis variability at Point 7 on the chemicalreagent test slide 4 (see FIG. 5 for the location of Target Point 7) isobtained.

As mentioned previously, the planar main body 8 of the Z-axismeasurement fixture 6 of the present disclosure may be 3D printed andformed in many different shapes to accommodate and hold planar objects 2of different shapes and sizes, including free form andirregularly-shaped objects 2. For example, and as shown in FIGS. 1, 1Aand 2 of the drawings, the measurement fixture 6 used for testingtrapezoidially-shaped chemical reagent test slides 4 may include one ormore object edge guide projections 38 extending outwardly from the topwall 12 of the planar main body 8. As shown in FIGS. 1 and 2, there aretwo, generally V-shaped wedge projections 40 spaced apart from eachother near opposite lateral sides 42 of the planar main body 8. Thesetwo wedge projections 40 are loosely received in notches 44 formed inopposite lateral side walls 46 of the trapezoidially-shaped chemicalreagent test slide 4 to help hold the slide 4 in place and in a properposition above the top wall 12 of the planar main body 8. Furthermore,the fixture 6 may include a third projection 48 spaced apart from thepair of wedge projections 40 and situated at a lower edge portion 50 ofthe planar main body 8 of the fixture 6. This third projection 48 isformed as a straight ledge and engages the larger rear wall 52 of thetrapezoidially-shaped chemical reagent test slide 4 so that the testslide 4 is held in place above the top wall 12 of the planar main body 8of the fixture 6 between the two wedge projections 40 and the lower,third projection 48 such that the test slide 4 does not move relative tothe fixture 6 in the X-Y plane.

The Z-axis measurement fixture 6 of the present disclosure holds theposition of the stainless steel balls 18 in the X-Y plane, yet allowsthe balls 18 to freely contact the part 4 and the known flat surface 34of the gauge block 30. The use of calibrated gauge balls 18 eliminatesthe need for tight tolerances on the spacer (i.e., the fixture 6 withits planar main body 8). This allows the part to be custom printed forthe application. The gauge balls 18 provide a known calibrated “Z”distance from the known flat surface 34 of the gauge block 30. Thecalibrated gauge balls 18 further enable the part 4 (e.g., a chemicalreagent test slide) to be positioned in space by consistently contactingthree target datums on the part 4.

The fixture 6 and method for measuring the degree of Z-axis variabilityor surface topography irregularities in a chemical reagent test slide 4,or more generally, object 2, will now be further described.

In one embodiment, the Z-axis measurement fixture 6 used for testingwhether a chemical reagent test slide 4 exhibits Z-axis variability orsurface topography irregularities, includes a main body 8, the main body8 having a top wall 12 and a bottom wall 14 disposed opposite the topwall 12, the main body 8 defining a plurality of member receivingopenings 16 extending between the top wall 12 and the bottom wall 14;and a plurality of test slide supporting members 10, each test slidesupporting member 10 of the plurality of test slide supporting members10 having a known and calibrated dimension in at least one coordinatedirection, each test slide supporting member 10 of the plurality of testslide supporting members 10 being received by a respective memberreceiving opening 16 of the plurality of member receiving openings 16defined by the main body 8, each test slide supporting member 10 of theplurality of test slide supporting members 10 having a first portion 20which projects outwardly from the top wall 12 of the main body 8 and asecond portion 22 which projects outwardly from or is at least levelwith the bottom wall 14 of the main body 8, each test slide supportingmember 10 of the plurality of test slide supporting members 10 beingarranged within the respective member receiving opening 16 of theplurality of member receiving openings 16 such that the first portion 20thereof projecting outwardly from the top wall 12 of the main body 8 andthe second portion 22 thereof projecting outwardly from or being levelwith the bottom wall 14 of the main body 8 are in alignment with theknown and calibrated dimension of the test slide supporting member 10 inthe at least one coordinate direction.

In one embodiment of the fixture 6, each test slide supporting member 10of the plurality of test slide supporting members 10 is a sphericalmember having a known and calibrated diameter.

In one embodiment of the fixture 6, each test slide supporting member 10of the plurality of test slide supporting members 10 is a stainlesssteel ball 18 having a known and calibrated diameter.

In one embodiment of the fixture 6, the plurality of test slidesupporting members 10 includes three test slide supporting members 10spaced apart from each other.

In one embodiment of the Z-axis measurement fixture 6, the first portion20 of each test slide supporting member 10 of the plurality of testslide supporting members 10 which projects outwardly from the top wall12 of the main body 8 is adapted to contact and support a portion of thechemical reagent test slide 4. In one embodiment of the fixture 6, thesecond portion 22 of each test slide supporting member 10 of theplurality of test slide supporting members 10 which projects outwardlyfrom or is level with the bottom wall 14 of the main body 8 is adaptedto contact a surface 34 of a gauge block 30 of a measurement instrument28.

In one embodiment of the Z-axis measurement fixture 6, the main body 8includes at least one test slide edge guide projection 38 extendingoutwardly from the top wall 12 thereof, the at least one test slide edgeguide projection 38 being provided to help locate the chemical reagenttest slide 4 in a proper position above the top wall 12 of the main body8.

In one embodiment of the Z-axis measurement fixture 6, the at least onetest slide edge guide projection 38 includes a first generally V-shapedwedge projection 40 and a second generally V-shaped wedge projection 40,the first wedge projection 40 being spaced apart from the second wedgeprojection 40 on the top wall 12 of the main body 8, the chemicalreagent test slide 4 being receivable between the first and second wedgeprojections 40.

In one embodiment of the Z-axis measurement fixture 6, the at least onetest slide edge guide projection 38 includes a first generally V-shapedwedge projection 40, a second generally V-shaped wedge projection 40 anda third projection 48, the first wedge projection 40 being spaced apartfrom the second wedge projection 40 on the top wall 12 of the main body8, the third projection 48 being spaced apart from the first wedgeprojection 40 and the second wedge projection 40 on the top wall 12 ofthe main body 8, the chemical reagent test slide 4 being receivablebetween the first and second wedge projections 40 and the thirdprojection 48.

Described herein is a method of measuring the degree of Z-axisvariability or surface topography irregularities in a chemical reagenttest slide 4. The chemical reagent test slide 4 has an upper surface 54and a lower surface 56 situated opposite the upper surface 54. Themethod includes the step of placing a Z-axis measurement fixture 6 on asurface 34 of a gauge block 30 of a measurement instrument 28, theZ-axis measurement fixture 6 having a main body 8 and a plurality oftest slide supporting members 10, the main body 8 having a top wall 12and a bottom wall 14 disposed opposite the top wall 12, the main body 8defining a plurality of member receiving openings 16 extending betweenthe top wall 12 and the bottom wall 14, each test slide supportingmember 10 of the plurality of test slide supporting members 10 having aknown and calibrated dimension in at least one coordinate direction,each test slide supporting member 10 of the plurality of test slidesupporting members 10 being received by a respective member receivingopening 16 of the plurality of member receiving openings 16 extending inthe main body 8, each test slide supporting member 10 of the pluralityof test slide supporting members 10 having a first portion 20 whichprojects outwardly from the top wall 12 of the main body 8 and a secondportion 22 which projects outwardly from or is at least level with thebottom wall 14 of the main body 8, each test slide supporting member 10of the plurality of the test slide supporting members 10 being arrangedwithin the respective member receiving opening 16 of the plurality ofmember receiving openings 16 such that the first portion 20 thereofprojecting outwardly from the top wall 12 of the main body 8 and thesecond portion 22 thereof projecting outwardly from or being level withthe bottom wall 14 of the main body 8 are in alignment with the knownand calibrated dimension of the test slide supporting member 10 in theat least one coordinate direction, wherein the second portion 22 of eachtest slide supporting member 10 of the plurality of test slidesupporting members 10 engages the surface 34 of the gauge block 30 ofthe measurement instrument 28.

In one embodiment, the method includes the step of mounting the chemicalreagent test slide 4 on the Z-axis measurement fixture 6 such that thechemical reagent test slide 4 rests on and is supported by the firstportion 20 of each test slide supporting member 10 of the plurality oftest slide supporting members 10.

In one embodiment, the method includes the step of positioning thechemical reagent test slide 4 mounted on the Z-axis measurement fixture6 on the measurement instrument 28.

In one embodiment, the method includes the step of determining by themeasurement instrument 28 the degree of Z-axis variability or surfacetopography irregularities in the chemical reagent test slide 4.

In one embodiment, a method of measuring the degree of Z-axisvariability or surface topography irregularities in a chemical reagenttest slide 4 is described herein. The chemical reagent test slide 4 hasan upper surface 54 and a lower surface 56 situated opposite the uppersurface 54. The method includes the step of placing a Z-axis measurementfixture 6 on a surface 34 of a gauge block 30 of an optical measurementinstrument 28, the Z-axis measurement fixture 6 having a main body 8 anda plurality of test slide supporting members 10, the main body 8 havinga top wall 12 and a bottom wall 14 disposed opposite the top wall 12,the main body 8 defining a plurality of member receiving openings 16extending between the top wall 12 and the bottom wall 14, each testslide supporting member 10 of the plurality of test slide supportingmembers 10 having a known and calibrated dimension in at least onecoordinate direction, each test slide supporting member 10 of theplurality of test slide supporting members 10 being received by arespective member receiving opening 16 of the plurality of memberreceiving openings 16 extending in the main body 8, each test slidesupporting member 10 of the plurality of test slide supporting members10 having a first portion 20 which projects outwardly from the top wall12 of the main body 8 and a second portion 22 which projects outwardlyfrom or is at least level with the bottom wall 14 of the main body 8,each test slide supporting member 10 of the plurality of the test slidesupporting members 10 being arranged within the respective memberreceiving opening 16 of the plurality of member receiving openings 16such that the first portion 20 thereof projecting outwardly from the topwall 12 of the main body 8 and the second portion 22 thereof projectingoutwardly from or being level with the bottom wall 14 of the main body 8are in alignment with the known and calibrated dimension of the testslide supporting member 10 in the at least one coordinate direction,wherein the second portion 22 of each test slide supporting member 10 ofthe plurality of test slide supporting members 10 engages the surface 34of the gauge block 30 of the optical measurement instrument 28, theoptical measurement instrument 28 further having a camera 32.

In one embodiment, the method includes the step of mounting the chemicalreagent test slide 4 on the Z-axis measurement fixture 6 such that thechemical reagent test slide 4 rests on and is supported by the firstportion 20 of each test slide supporting member 10 of the plurality oftest slide supporting members 10.

In one embodiment, the method includes the step of positioning thechemical reagent test slide 4 mounted on the Z-axis measurement fixture6 in optical communication with the camera 32 of the optical measurementinstrument 28.

In one embodiment, the method includes the step of imaging the chemicalreagent test slide 4 using the camera 32 of the optical measurementinstrument 28 having a predetermined field of view at a first focalpoint or first focal area on an imaged surface of the chemical reagenttest slide 4 to provide a first optical image of the chemical reagenttest slide 4 in which the first focal point or first focal area on theimaged surface of the chemical reagent test slide 4 is in focus in thefirst optical image, the first optical image being in a first X-Y planein which the first focal point or first focal area, in focus in thefirst optical image, resides, the first X-Y plane establishing a zeroreference plane for measuring the degree of Z-axis variability orsurface topography irregularities in the chemical reagent test slide 4.

In one embodiment, the method includes the step of imaging the chemicalreagent test slide 4 using the camera 32 of the optical measurementinstrument 28 at at least a second focal point or second focal area onthe imaged surface of the chemical reagent test slide 4 which is spacedfrom the first focal point or first focal area to provide at least asecond optical image of the chemical reagent test slide 4 in which theat least second focal point or second focal area is in focus in the atleast second optical image, the at least second optical image being inan at least second X-Y plane in which the at least second focal point orsecond focal area, in focus in the at least second optical image,resides.

In one embodiment, the method includes the step of measuring therelative distance in the Z-axis between the zero reference plane and theat least second X-Y plane to provide a measured relative distance.

In one embodiment, the method includes the step of determining from themeasured relative distance the degree of Z-axis variability or surfacetopography irregularities in the chemical reagent test slide 4.

In one embodiment, a method of measuring the degree of Z-axisvariability or surface topography irregularities in an object 2 to betested is described herein. The object 2 to be tested has an uppersurface 54 and a lower surface 56 situated opposite the upper surface54. The method includes the step of placing a Z-axis measurement fixture6 on a surface 34 of a gauge block 30 of an optical measurementinstrument 28, the Z-axis measurement fixture 6 having a main body 8 anda plurality of object supporting members 10, the main body 8 having atop wall 12 and a bottom wall 14 disposed opposite the top wall 12, themain body 8 defining a plurality of member receiving openings 16extending between the top wall 12 and the bottom wall 14, each objectsupporting member 10 of the plurality of object supporting members 10having a known and calibrated dimension in at least one coordinatedirection, each object supporting member 10 of the plurality of objectsupporting members 10 being received by a respective member receivingopening 16 of the plurality of member receiving openings 16 extending inthe main body 8, each object supporting member 10 of the plurality ofobject supporting members 10 having a first portion 20 which projectsoutwardly from the top wall 12 of the main body 8 and a second portion22 which projects outwardly from or is at least level with the bottomwall 14 of the main body 8, each object supporting member 10 of theplurality of object supporting members 10 being arranged within therespective member receiving opening 16 of the plurality of memberreceiving openings 16 such that the first portion 20 thereof projectingoutwardly from the top wall 12 of the main body 8 and the second portion22 thereof projecting outwardly from or being level with the bottom wall14 of the main body 8 are in alignment with the known and calibrateddimension of the object supporting member 10 in the at least onecoordinate direction, wherein the second portion 22 of each objectsupporting member 10 of the plurality of the object supporting members10 engages the surface 34 of the gauge block 30 of the opticalmeasurement instrument 28, the optical measurement instrument 28 furtherhaving a camera 32.

In one embodiment, the method includes the step of mounting the object 2to be tested on the Z-axis measurement fixture 6 such that the object 2to be tested rests on and is supported by the first portion 20 of eachobject supporting member 10 of the plurality of object supportingmembers 10.

In one embodiment, the method includes the step of positioning theobject 2 to be tested mounted on the Z-axis measurement fixture 6 inoptical communication with the camera 32 of the optical measurementinstrument 28.

In one embodiment, the method includes the step of imaging the object 2to be tested using the camera 32 of the optical measurement instrument28 having a predetermined field of view at a first focal point or firstfocal area on an imaged surface of the object 2 to be tested to providea first optical image of the object 2 in which the first focal point orfirst focal area on the imaged surface of the object 2 is in focus inthe first optical image, the first optical image being in a first X-Yplane in which the first focal point or first focal area, in focus inthe first optical image, resides, the first X-Y plane establishing azero reference plane for measuring the degree of Z-axis variability orsurface topography irregularities in the object 2.

In one embodiment, the method includes the step of successively imagingthe object 2 to be tested using the camera 32 of the optical measurementinstrument 28 at successive spaced apart focal points or focal areas onthe imaged surface of the object 2 to provide successive optical imagesof the object 2 in which the successive focal points or focal areas arerespectively in focus, the successive optical images being in opticalX-Y planes in which the respective focal points or focal areas resideand are in focus.

In one embodiment, the method includes the step of determining whetherone or more of the optical X-Y planes are above the zero reference planerelative to the Z-axis and whether one or more of the optical X-Y planesis below the zero reference plane relative to the Z-axis.

In one embodiment, the method includes the step of measuring therelative distances in the Z-axis between the zero reference plane andeach successive optical X-Y plane to provide a plurality of measuredrelative distances.

In one embodiment of the method, when all of the successive optical X-Yplanes are situated above the zero reference plane, the method includesthe steps of determining which of the measured relative distances is thegreatest relative distance above the zero reference plane anddetermining the degree of Z-axis variability or surface topographyirregularities in the object 2 from the greatest relative distance abovethe zero reference plane.

In one embodiment of the method, when all of the successive optical X-Yplanes are situated below the zero reference plane, the method includesthe steps of determining which of the measured relative distances is thegreatest relative distance below the zero reference plane anddetermining the degree of Z-axis variability or surface topographyirregularities in the object 2 from the greatest relative distance belowthe zero reference plane.

In one embodiment of the method, when one or more of the successiveoptical X-Y planes are situated above the zero reference plane and oneor more of the successive optical X-Y planes are situated below the zeroreference plane, the method includes the steps of determining which ofthe measured relative distances for the successive optical X-Y planesabove the zero reference plane is the greatest measured distance abovethe zero reference plane and determining which of the measured relativedistances for the successive optical X-Y planes below the zero referenceplane is the greatest measured distance below the zero reference planeand determining the degree of Z-axis variability or surface topographyirregularities in the object 2 from the greatest measured distance abovethe zero reference plane and the greatest measured distance below thezero reference plane.

In one embodiment of the method, each object supporting member 10 of theplurality of object supporting members 10 of the Z-axis measurementfixture 6 is a spherical member having a known and calibrated diameter.

In one embodiment of the method, each object supporting member 10 of theplurality of object supporting members 10 of the Z-axis measurementfixture 6 is a stainless steel ball 18 having a known and calibrateddiameter.

In one embodiment of the method, the plurality of object supportingmembers 10 of the Z-axis measurement fixture 6 includes three objectsupporting members 10 spaced apart from each other.

In one embodiment of the method, the main body 8 of the Z-axismeasurement fixture 6 includes at least one object edge guide projection38 extending outwardly from the top wall 12 thereof, the at least oneobject edge guide projection 38 being provided to help locate the object2 to be tested in a proper position above the top wall 12 of the mainbody 8.

In one embodiment of the method, the at least one object edge guideprojection 38 of the fixture 6 includes a first generally V-shaped wedgeprojection 40 and a second generally V-shaped wedge projection 40, thefirst wedge projection 40 being spaced apart from the second wedgeprojection 40 on the top wall 12 of the main body 8 of the fixture 6,wherein the object 2 to be tested is receivable between the first andsecond wedge projections 40.

In one embodiment of the method, the at least one object edge guideprojection 38 of the fixture 6 includes a first generally V-shaped wedgeprojection 40, a second generally V-shaped wedge projection 40 and athird projection 48, the first wedge projection 40 being spaced apartfrom the second wedge projection 40 on the top wall 12 of the main body8 of the fixture 6, the third projection 48 being spaced apart from thefirst wedge projection 40 and the second wedge projection 40 on the topwall 12 of the main body 8, wherein the object 2 to be tested isreceivable between the first and second wedge projections 40 and thethird projection 48.

Although illustrative embodiments of the present disclosure have beendescribed herein with reference to the accompanying drawings, it is tobe understood that the disclosure is not limited to those preciseembodiments, and that various other changes and modifications may beeffected therein by one skilled in the art without departing from thescope or spirit of the disclosure.

What is claimed is:
 1. A Z-axis measurement fixture used for testingwhether a chemical reagent test slide exhibits Z-axis variability orsurface topography irregularities, which comprises: a main body, themain body having a top wall and a bottom wall disposed opposite the topwall, the main body defining a plurality of member receiving openingsextending between the top wall and the bottom wall; and a plurality oftest slide supporting members, each test slide supporting member of theplurality of test slide supporting members having a known and calibrateddimension in at least one coordinate direction, each test slidesupporting member of the plurality of test slide supporting membersbeing received by a respective member receiving opening of the pluralityof member receiving openings defined by the main body, each test slidesupporting member of the plurality of test slide supporting membershaving a first portion which projects outwardly from the top wall of themain body and a second portion which projects outwardly from or is atleast level with the bottom wall of the main body, each test slidesupporting member of the plurality of test slide supporting membersbeing arranged within the respective member receiving opening of theplurality of member receiving openings such that the first portionthereof projecting outwardly from the top wall of the main body and thesecond portion thereof projecting outwardly from or being level with thebottom wall of the main body are in alignment with the known andcalibrated dimension of the test slide supporting member in the at leastone coordinate direction.
 2. A Z-axis measurement fixture as defined byclaim 1, wherein each test slide supporting member of the plurality oftest slide supporting members is a spherical member having a known andcalibrated diameter.
 3. A Z-axis measurement fixture as defined by claim1, wherein each test slide supporting member of the plurality of testslide supporting members is a stainless steel ball having a known andcalibrated diameter.
 4. A Z-axis measurement fixture as defined by claim1, wherein the plurality of test slide supporting members includes threetest slide supporting members spaced apart from each other.
 5. A Z-axismeasurement fixture as defined by claim 1, wherein the first portion ofeach test slide supporting member of the plurality of test slidesupporting members which projects outwardly from the top wall of themain body is adapted to contact and support a portion of the chemicalreagent test slide; and wherein the second portion of each test slidesupporting member of the plurality of test slide supporting memberswhich projects outwardly from or is level with the bottom wall of themain body is adapted to contact a surface of a gauge block of ameasurement instrument.
 6. A Z-axis measurement fixture as defined byclaim 1, wherein the main body includes at least one test slide edgeguide projection extending outwardly from the top wall thereof, the atleast one test slide edge guide projection being provided to help locatethe chemical reagent test slide in a proper position above the top wallof the main body.
 7. A Z-axis measurement fixture as defined by claim 6,wherein the at least one test slide edge guide projection includes afirst generally V-shaped wedge projection and a second generallyV-shaped wedge projection, the first wedge projection being spaced apartfrom the second wedge projection on the top wall of the main body; andwherein the chemical reagent test slide is receivable between the firstand second wedge projections.
 8. A Z-axis measurement fixture as definedby claim 6, wherein the at least one test slide edge guide projectionincludes a first generally V-shaped wedge projection, a second generallyV-shaped wedge projection and a third projection, the first wedgeprojection being spaced apart from the second wedge projection on thetop wall of the main body, the third projection being spaced apart fromthe first wedge projection and the second wedge projection on the topwall of the main body; and wherein the chemical reagent test slide isreceivable between the first and second wedge projections and the thirdprojection.
 9. A method of measuring the degree of Z-axis variability orsurface topography irregularities in a chemical reagent test slide, thechemical reagent test slide having an upper surface and a lower surfacesituated opposite the upper surface, the method comprising the steps of:placing a Z-axis measurement fixture on a surface of a gauge block of ameasurement instrument, the Z-axis measurement fixture having a mainbody and a plurality of test slide supporting members, the main bodyhaving a top wall and a bottom wall disposed opposite the top wall, themain body defining a plurality of member receiving openings extendingbetween the top wall and the bottom wall, each test slide supportingmember of the plurality of test slide supporting members having a knownand calibrated dimension in at least one coordinate direction, each testslide supporting member of the plurality of test slide supportingmembers being received by a respective member receiving opening of theplurality of member receiving openings extending in the main body, eachtest slide supporting member of the plurality of test slide supportingmembers having a first portion which projects outwardly from the topwall of the main body and a second portion which projects outwardly fromor is at least level with the bottom wall of the main body, each testslide supporting member of the plurality of the test slide supportingmembers being arranged within the respective member receiving opening ofthe plurality of member receiving openings such that the first portionthereof projecting outwardly from the top wall of the main body and thesecond portion thereof projecting outwardly from or being level with thebottom wall of the main body are in alignment with the known andcalibrated dimension of the test slide supporting member in the at leastone coordinate direction, wherein the second portion of each test slidesupporting member of the plurality of test slide supporting membersengages the surface of the gauge block of the measurement instrument;mounting the chemical reagent test slide on the Z-axis measurementfixture such that the chemical reagent test slide rests on and issupported by the first portion of each test slide supporting member ofthe plurality of test slide supporting members; positioning the chemicalreagent test slide mounted on the Z-axis measurement fixture on themeasurement instrument; and determining by the measurement instrumentthe degree of Z-axis variability or surface topography irregularities inthe chemical reagent test slide.
 10. A method of measuring the degree ofZ-axis variability or surface topography irregularities in a chemicalreagent test slide, the chemical reagent test slide having an uppersurface and a lower surface situated opposite the upper surface, themethod comprising the steps of: placing a Z-axis measurement fixture ona surface of a gauge block of an optical measurement instrument, theZ-axis measurement fixture having a main body and a plurality of testslide supporting members, the main body having a top wall and a bottomwall disposed opposite the top wall, the main body defining a pluralityof member receiving openings extending between the top wall and thebottom wall, each test slide supporting member of the plurality of testslide supporting members having a known and calibrated dimension in atleast one coordinate direction, each test slide supporting member of theplurality of test slide supporting members being received by arespective member receiving opening of the plurality of member receivingopenings extending in the main body, each test slide supporting memberof the plurality of test slide supporting members having a first portionwhich projects outwardly from the top wall of the main body and a secondportion which projects outwardly from or is at least level with thebottom wall of the main body, each test slide supporting member of theplurality of the test slide supporting members being arranged within therespective member receiving opening of the plurality of member receivingopenings such that the first portion thereof projecting outwardly fromthe top wall of the main body and the second portion thereof projectingoutwardly from or being level with the bottom wall of the main body arein alignment with the known and calibrated dimension of the test slidesupporting member in the at least one coordinate direction, wherein thesecond portion of each test slide supporting member of the plurality oftest slide supporting members engages the surface of the gauge block ofthe optical measurement instrument, the optical measurement instrumentfurther having a camera; mounting the chemical reagent test slide on theZ-axis measurement fixture such that the chemical reagent test sliderests on and is supported by the first portion of each test slidesupporting member of the plurality of test slide supporting members; andpositioning the chemical reagent test slide mounted on the Z-axismeasurement fixture in optical communication with the camera of theoptical measurement instrument.
 11. A method as defined by claim 10,which further comprises the step of: imaging the chemical reagent testslide using the camera of the optical measurement instrument having apredetermined field of view at a first focal point or first focal areaon an imaged surface of the chemical reagent test slide to provide afirst optical image of the chemical reagent test slide in which thefirst focal point or first focal area on the imaged surface of thechemical reagent test slide is in focus in the first optical image, thefirst optical image being in a first X-Y plane in which the first focalpoint or first focal area, in focus in the first optical image, resides,the first X-Y plane establishing a zero reference plane for measuringthe degree of Z-axis variability or surface topography irregularities inthe chemical reagent test slide.
 12. A method as defined by claim 11,which further comprises the step of: imaging the chemical reagent testslide using the camera of the optical measurement instrument at at leasta second focal point or second focal area on the imaged surface of thechemical reagent test slide which is spaced from the first focal pointor first focal area to provide at least a second optical image of thechemical reagent test slide in which the at least second focal point orsecond focal area is in focus in the at least second optical image, theat least second optical image being in an at least second X-Y plane inwhich the at least second focal point or second focal area, in focus inthe at least second optical image, resides.
 13. A method as defined byclaim 12, which further comprises the step of: measuring the relativedistance in the Z-axis between the zero reference plane and the at leastsecond X-Y plane to provide a measured relative distance.
 14. A methodas defined by claim 13, which further comprises the step of: determiningfrom the measured relative distance the degree of Z-axis variability orsurface topography irregularities in the chemical reagent test slide.15. A method as defined by claim 10, wherein each test slide supportingmember of the plurality of test slide supporting members of the Z-axismeasurement fixture is a spherical member having a known and calibrateddiameter.
 16. A method as defined by claim 10, wherein each test slidesupporting member of the plurality of test slide supporting members ofthe Z-axis measurement fixture is a stainless steel ball having a knownand calibrated diameter.
 17. A method as defined by claim 10, whereinthe plurality of test slide supporting members of the Z-axis measurementfixture includes three test slide supporting members spaced apart fromeach other.
 18. A method as defined by claim 10, wherein the main bodyof the Z-axis measurement fixture includes at least one test slide edgeguide projection extending outwardly from the top wall thereof, the atleast one test slide edge guide projection being provided to help locatethe chemical reagent test slide in a proper position above the top wallof the main body.
 19. A method as defined by claim 18, wherein the atleast one test slide edge guide projection includes a first generallyV-shaped wedge projection and a second generally V-shaped wedgeprojection, the first wedge projection being spaced apart from thesecond wedge projection on the top wall of the main body; and whereinthe chemical reagent test slide is receivable between the first andsecond wedge projections.
 20. A method as defined by claim 18, whereinthe at least one test slide edge guide projection includes a firstgenerally V-shaped wedge projection, a second generally V-shaped wedgeprojection and a third projection, the first wedge projection beingspaced apart from the second wedge projection on the top wall of themain body, the third projection being spaced apart from the first wedgeprojection and the second wedge projection on the top wall of the mainbody; and wherein the chemical reagent test slide is receivable betweenthe first and second wedge projections and the third projection.
 21. Amethod of measuring the degree of Z-axis variability or surfacetopography irregularities in an object to be tested, the object to betested having an upper surface and a lower surface situated opposite theupper surface, the method comprising the steps of: placing a Z-axismeasurement fixture on a surface of a gauge block of an opticalmeasurement instrument, the Z-axis measurement fixture having a mainbody and a plurality of object supporting members, the main body havinga top wall and a bottom wall disposed opposite the top wall, the mainbody defining a plurality of member receiving openings extending betweenthe top wall and the bottom wall, each object supporting member of theplurality of object supporting members having a known and calibrateddimension in at least one coordinate direction, each object supportingmember of the plurality of object supporting members being received by arespective member receiving opening of the plurality of member receivingopenings extending in the main body, each object supporting member ofthe plurality of object supporting members having a first portion whichprojects outwardly from the top wall of the main body and a secondportion which projects outwardly from or is at least level with thebottom wall of the main body, each object supporting member of theplurality of object supporting members being arranged within therespective member receiving opening of the plurality of member receivingopenings such that the first portion thereof projecting outwardly fromthe top wall of the main body and the second portion thereof projectingoutwardly from or being level with the bottom wall of the main body arein alignment with the known and calibrated dimension of the objectsupporting member in the at least one coordinate direction, wherein thesecond portion of each object supporting member of the plurality of theobject supporting members engages the surface of the gauge block of theoptical measurement instrument, the optical measurement instrumentfurther having a camera; mounting the object to be tested on the Z-axismeasurement fixture such that the object to be tested rests on and issupported by the first portion of each object supporting member of theplurality of object supporting members; positioning the object to betested mounted on the Z-axis measurement fixture in opticalcommunication with the camera of the optical measurement instrument;imaging the object to be tested using the camera of the opticalmeasurement instrument having a predetermined field of view at a firstfocal point or first focal area on an imaged surface of the object to betested to provide a first optical image of the object in which the firstfocal point or first focal area on the imaged surface of the object isin focus in the first optical image, the first optical image being in afirst X-Y plane in which the first focal point or first focal area, infocus in the first optical image, resides, the first X-Y planeestablishing a zero reference plane for measuring the degree of Z-axisvariability or surface topography irregularities in the object;successively imaging the object to be tested using the camera of theoptical measurement instrument at successive spaced apart focal pointsor focal areas on the imaged surface of the object to provide successiveoptical images of the object in which the successive focal points orfocal areas are respectively in focus, the successive optical imagesbeing in optical X-Y planes in which the respective focal points orfocal areas reside and are in focus.
 22. A method as defined by claim21, which further comprises the step of: determining whether one or moreof the optical X-Y planes are above the zero reference plane relative tothe Z-axis and whether one or more of the optical X-Y planes is belowthe zero reference plane relative to the Z-axis.
 23. A method as definedby claim 22, which further comprises the steps of: measuring therelative distances in the Z-axis between the zero reference plane andeach successive optical X-Y plane to provide a plurality of measuredrelative distances; wherein, when all of the successive optical X-Yplanes are situated above the zero reference plane, determining which ofthe measured relative distances is the greatest relative distance abovethe zero reference plane and determining the degree of Z-axisvariability or surface topography irregularities in the object from thegreatest relative distance above the zero reference plane; wherein, whenall of the successive optical X-Y planes are situated below the zeroreference plane, determining which of the measured relative distances isthe greatest relative distance below the zero reference plane anddetermining the degree of Z-axis variability or surface topographyirregularities in the object from the greatest relative distance belowthe zero reference plane; and wherein, when one or more of thesuccessive optical X-Y planes are situated above the zero referenceplane and one or more of the successive optical X-Y planes are situatedbelow the zero reference plane, determining which of the measuredrelative distances for the successive optical X-Y planes above the zeroreference plane is the greatest measured distance above the zeroreference plane and determining which of the measured relative distancesfor the successive optical X-Y planes below the zero reference plane isthe greatest measured distance below the zero reference plane anddetermining the degree of Z-axis variability or surface topographyirregularities in the object from the greatest measured distance abovethe zero reference plane and the greatest measured distance below thezero reference plane.
 24. A method as defined by claim 21, wherein eachobject supporting member of the plurality of object supporting membersof the Z-axis measurement fixture is a spherical member having a knownand calibrated diameter.
 25. A method as defined by claim 21, whereineach object supporting member of the plurality of object supportingmembers of the Z-axis measurement fixture is a stainless steel ballhaving a known and calibrated diameter.
 26. A method as defined by claim21, wherein the plurality of object supporting members of the Z-axismeasurement fixture includes three object supporting members spacedapart from each other.
 27. A method as defined by claim 21, wherein themain body of the Z-axis measurement fixture includes at least one objectedge guide projection extending outwardly from the top wall thereof, theat least one object edge guide projection being provided to help locatethe object to be tested in a proper position above the top wall of themain body.
 28. A method as defined by claim 27, wherein the at least oneobject edge guide projection includes a first generally V-shaped wedgeprojection and a second generally V-shaped wedge projection, the firstwedge projection being spaced apart from the second wedge projection onthe top wall of the main body; and wherein the object to be tested isreceivable between the first and second wedge projections.
 29. A methodas defined by claim 27, wherein the at least one object edge guideprojection includes a first generally V-shaped wedge projection, asecond generally V-shaped wedge projection and a third projection, thefirst wedge projection being spaced apart from the second wedgeprojection on the top wall of the main body, the third projection beingspaced apart from the first wedge projection and the second wedgeprojection on the top wall of the main body; and wherein the object tobe tested is receivable between the first and second wedge projectionsand the third projection.